Flame retardants are incorporated into many products for safety in efforts to control the spread of fire through the product. Flame retardants can, for example, act by causing rapid extinguishing of flames, or by making the product difficult to set afire. While flame retardants have conventionally been used to treat fabrics, soft furnishings, etc. and have been incorporated into foams, paints, and resins such as epoxy resins, many other applications are now being actively pursued, especially within the electronic, automotive, aerospace and construction industries.
Although useful in providing flame retardant properties in thermoplastics, known phosphonate flame retardant additives have disadvantages which limit their use. The present invention provides a phosphonate flame retardant additive which avoids the disadvantages of the known phosphonate flame retardant additives to provide useful compositions.
One disadvantage of the known phosphonate flame retardant additives is that the known flame retardant additives impart a variety of performance problems and other deficiencies to the thermoplastic composition. These problems can limit or eliminate their usefulness with some thermoplastics and in particular, polyolefins. Off-gassing and liquid bleed out in particular have been found in these thermoplastic systems and these disadvantages are believed to have been caused by phosphonate salt/synergist interactions.
Many of the conventional flame retardant additives have been found to have a tendency to migrate and/or volatilize from the thermoplastics over time. The migration of the flame retardant additive causes the object to eventually lose its flame retardant properties. Yet another disadvantage of known phosphonate flame retardants additives are their hygroscopic properties, which will cause thermoplastic objects incorporating these additives to absorb moisture or water over time. Furthermore the known phosphonate flame retardant additives have poor thermal stability. The additives are known to decompose at various thermoplastic processing temperatures, and particularly during the thermoplastic extrusion process.
The present invention seeks to overcome the disadvantages of conventional additives by providing a more stable phosphonate flame retardant additive.